Evaluation And Application Of Reprojection Methods For 3D PET

This paper reviews the various methods of sinogram calculation or reprojection and those appropriate for 3D PET. Then a rapid calculation method that utilizes the 8fold 2D symmetry of the PET data for single sinogram calculations is introduced to 3D. Two ray-tracing methods that differ in their model of the voxel are implemented and their speed-up measured using the rapid calculation method. The first voxel model assumes parallelepiped shaped discrete voxels and the second model approximates the data as a sampled continuous distribution. The two ray-tracing methods of reprojection are compared on phantom data for their resolution loss and sampling error. Each method is applied to the problem of attenuation correction factor calculation, both 3D from regions of interest geometry data and 3D from 2D, then compared with measured attenuation correction data. Due to its simplicity and speed the parallelepiped voxel method is recommended for use in 3D PET algorithms and the associated error is characterized.